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View Full Version : Knock issues and looking for insight. Bring it on your logging gurus!



MADMarc
01-22-2011, 01:22 AM
19091910

I am at about 7k on some NGK coppers. Just swapped out my coil packs because the car has 170k, I never replaced them during the motor swap and couldn't find any receipts from the previous owner stating that it was ever done. Also, before I was having some nasty stuttering around 11 psi at higher RPMs under a load so figured why the hell not replace the packs.

I understand that the plugs are nearing their swap out time and I also know of one small boost leak (damn clutch booster line is hard as a rock) but my o2 voltages don't look drastic to me. What do you guys think? I am still terribly new at this manipulating my logs thing.

Roybatty
01-22-2011, 07:55 AM
My knocking was fuel related; went with a walbro and always use 91 or higher.

MADMarc
01-22-2011, 07:07 PM
But My thing is that if it were fuel related wouldn't it show on the trim? Could it still be a spark issue? I did feel slight studdering but not as bad as it used to be before swapping the coils.

MADMarc
01-22-2011, 10:33 PM
Thanks for the input, Steve. I had problems when I gapped them to 32 so I bumped it to 38 (when the plugs were new) and the car ran fantastic until the recent issue. When I get back home I will check the sensors to make sure they fluctuate like they should.

OhioSpyderman
01-23-2011, 11:57 AM
I could be WAY off here, but shouldn't your Air Volume be something other than 0?

Is that not the frequency reading from the MAF?

It's been a while since I've done any logging, so forgive me if my head is up my A$$ :)

Bob.

RealMcCoy
01-23-2011, 01:08 PM
But My thing is that if it were fuel related wouldn't it show on the trim? Could it still be a spark issue? I did feel slight studdering but not as bad as it used to be before swapping the coils.

No.. Your issue is at WOT, the ECU is ignoring the O2 sensors and trim at that point. Providing your O2 sensors are working properly, and that the 0.9 I'm seeing on both sensors is truly 0.90, that's too lean.

But if you still have a misfire going on, you can't trust your O2 sensors anyway...


I could be WAY off here, but shouldn't your Air Volume be something other than 0?

Is that not the frequency reading from the MAF?

It's been a while since I've done any logging, so forgive me if my head is up my A$$ :)

Bob.

Correct... But I expect it's a logger or database translation error. It does appear to be correctly calculating load, which requires the airflow signal.

MADMarc
01-23-2011, 02:58 PM
Taking that into consideration and if it IS actually a fuel issue, then since both the front and rear banks are reading similar voltages (also considering that they are working correctly) how would I go about taking care of things? I have a denso 1020 as well as an AFPR but wasn't planning to toss them in until I got turbos. I don't expect it to harm anything if I do so and it would eliminate a possible fuel pump issue allowing me to log further to either eliminate that from my list or mitigate the knock entirely. Now, if it isn't the fuel pump, how can I go about testing the injectors? The filter was replaced when I did the swap so it has about 25k on it.

RealMcCoy
01-23-2011, 03:01 PM
Is the car all stock at the moment?

MADMarc
01-23-2011, 03:29 PM
For the most part. There are some simple goodies like the y-pipe, exhaust, profec spec II EBC, FIPK, fmic, fuel loop yadda yadda but nothing serious like fuel management or upgraded turbos.

RealMcCoy
01-23-2011, 03:42 PM
I'd want to get a fuel pressure gauge on it. A simple hotwire of the pump may be all that's needed in this case.

MADMarc
01-23-2011, 08:04 PM
Oooph I also have it hotwired. I know how to hook up a pressure gauge with the factory setup but since my problem is at higher rpms how could I monitor if its supplying adequate pressure in the higher rpms?

RealMcCoy
01-23-2011, 10:16 PM
Oooph I also have it hotwired. I know how to hook up a pressure gauge with the factory setup but since my problem is at higher rpms how could I monitor if its supplying adequate pressure in the higher rpms?

You need a pressure guage with a long enough hose to reach the windshield area, or an electronic gauge you can get inside with you.

You need to be able to tell if you're getting proper boost pressure rise. (1 lb of pressure for every lb of boost)

MADMarc
01-23-2011, 11:09 PM
So then the probability of it being the sensors is just about out. I could only imagine running a line to my window with my mechanical gauge :D if I set the Denso to the correct idle pressure I'm assuming my aem afpr would allow for the same pressure increase under boost? I will be swapping the plugs again soon as I am nearing the 10k mark and will nudge myself into dropping in the new pump considering I have everything to do so...just need to accept it if I break my factory lines in the proces. Thanks for the help.

RL7
01-24-2011, 08:01 PM
It's probably a bad fuel pump or wiring. Fuel pressure gauge is the best way to start. May want to check voltage to the pump itself (inside the tank).

MADMarc
01-24-2011, 08:38 PM
I don't expect anybody on here to have a solid number but does anyone know the likelihood of injectors failing or becoming so inaccurate from one another that it can cause problems like this?

NOMIEZVR4
01-25-2011, 01:24 AM
Have you actually pressure tested the car with a boost leak tester or are you just assuming it has no leaks other than the brake booster hose?

A smaller gap in your spark plugs shouldn't(32) in your case absolutely should not cause the problem to get worse. If anything, because the spark has to jump a smaller distance it should make your ignition system more effective(but combustion may slightly suffer because of a smaller spark).

Start with the absolute basics. Make sure you're running good octane fuel, change your plugs because you are stating yourself that they are due up to be changed, a tune-up as well if you haven't done one for a while. When you cant question your foundation of your mods, then you can move up the ladder and start looking at more complex issues like fuel pressure, etc...:)

Nomie

MADMarc
01-25-2011, 01:31 AM
I have pressure tested, found one serious leak and as soon as I got the correct hose in to fix it I discovered there is another leak that is far less serious but still evident. I want to say the problem with the narrower gap was that it was not sparking hot enough or long enough. Originally when I had the gap to .032 the problem studdering was as soon as I passed wastegate boost, this went away as soon as I upped it to .038 allowing for a larger kernel, i suppose, allowed for more combustion thus eliminating the issue - for the time being.

I will snag some new plugs HOPEFULLY this weekend and toss them in there. I never run less than 91 octane and the car doesn't have enough miles to justify doing a tune up. So long as my timing is good right now I want to leave that alone rather than spending hundreds more on parts that may only potentially take care of the problem. GAWDANGIT! It has to be a spark or fuel issue! lol Thanks for the responses guys.